Radio system having additional signalling channel dedicated for user data transmission otherwise carried on control channel

Abstract

A radio system and a method of transmitting data in a radio system, in which each base station has a radio channel operating as a call channel for signalling between the base station and mobile radio stations. User data can be transmitted on control channels among the actual control signalling, but the data transmission may block the control channel and prevent the normal operation of the control channel. The radio system includes for the user data transmission at least one radio channel operating like a control channel, but transmitting signalling that prevents the mobile stations from selecting the radio channel as a control channel.

I claim: 
     
       1. A radio system, comprising a plurality of mobile radio stations,   a base station,   a mobile exchange,   a first radio channel dedicated to operating only as a control channel for signalling control messages between said base station and said mobile stations and for transmitting user data messages, said control messages transmitted on said control channel by said base station including a first system code indicating to said plurality of mobile stations that said first radio channel is a control channel,   a second radio channel dedicated to operating only as an additional signalling channel for transmitting user data messages and control messages and operating according to the same protocol as said first radio channel, said control messages transmitted on said additional signalling channel by said base station including a second system code indicating to said plurality of mobile stations that said second radio channel is not a control channel,   said first radio channel being capable of operating as a control channel while said second radio channel is transmitting user data messages.   
     
     
       2. A radio system, comprising a plural of mobile radio stations,   a base station,   a mobile exchange,   a first radio channel dedicated to operating only as a control channel for signalling control messages between said base station and said mobile stations and for transmitting user data messages, said control messages transmitted on said control channel by said base station including a first system code indicating to said plurality of mobile stations that said first radio channel is a control channel,   a second radio channel dedicated to operating only as an additional signalling channel for transmitting user data messages and control messages and operating according to the same protocol as said first radio channel, said control messages transmitted on said additional signalling channel by said base station including a second system code indicating to said plurality of mobile stations that said second radio channel is not a control channel,   said mobile exchange being responsive to a user data transmission request transmitted by one of said plurality of mobile stations on said control channel for commanding said one of said plurality of mobile stations to said additional signalling channel for user data transmission,   said mobile exchange being responsive to the end of the user data transmission on said additional signalling channel for commanding said one of said plurality of mobile radio stations to return to said control channel,   said first radio channel being capable of operating as a control channel while said second radio channel is transmitting user data messages.   
     
     
       3. A data transmission method in a radio system, comprising steps of providing a first radio channel dedicated to and operating only as a control channel for signalling control messages between a base station and a plurality of mobile stations and for transmitting user data messages,   providing a second radio channel dedicated to and operating only as an additional signalling channel for transmitting user data messages and control messages and operating according to the same protocol as said first radio channel,   providing said control messages transmitted on said control channel with a first system code indicating to said plurality of mobile stations that said first radio channel is a control channel,   providing said control messages transmitted on said additional signalling channel with a second system code indicating to said plurality of mobile stations that said second radio channel is not a control channel,   transmitting a user data transmission request from one of said plurality of mobile radio stations on said control channel,   transmitting from said base station to said one of said plurality of mobile radio stations on said control channel a command to go to said additional signalling channel,   transmitting a user data transmission grant message from said base station to said one of said plurality of mobile radio stations on said additional signalling channel,   carrying out a user data transmission on said additional signalling channel, while transmitting control messaging on said control channel.   
     
     
       4. A method according to claim 3, comprising step of checking the availability of a called party prior to said step of transmitting said command. 
     
     
       5. A method according to claim 3, comprising a further step of allowing two or more of said mobile radio stations to simultaneously communicate on said additional signalling channel.   
     
     
       6. A method according to claim 5, comprising a further step of controlling the number of said mobile radio stations which communicate simultaneously on said additional signalling channel in such a way that an effective transmission rate per a mobile radio station on said additional signalling channel is equal to or higher than a predetermined threshold.   
     
     
       7. A method according to claim 3, comprising further steps of detecting end of the user data transmission on said additional signalling channel,   transmitting from said base station to said one of said plurality of mobile radio stations on said additional signalling channel a command to go back to said control channel.   
     
     
       8. A method according to claim 3, comprising further steps of detecting end of the user data transmission on said additional signalling channel, allowing said one of said plurality of mobile stations to stay on said additional signalling channel for a limited period of time in order to wait for a new user data transmission.   
     
     
       9. A data transmission method in a radio system, comprising steps of providing a first radio channel dedicated to and operating only as a control channel for signalling control messages between a base station and a plurality of mobile stations and for transmitting user data messages,   providing a second radio channel dedicated to and operating only as an additional signalling channel for transmitting user data messages and control messages and operating according to the same protocol as said first radio channel,   providing said control messages transmitted on said control channel with a first system code indicating to said plurality of mobile stations that said first radio channel is a control channel,   providing said control messages transmitted on said additional signalling channel with a second system code indicating to said plurality of mobile stations that said second radio channel is not a control channel,   transmitting a user data transmission request from said base station to one of said plurality of mobile radio stations on said control channel,   transmitting a user data transmission acknowledgement message from said one of said plurality of mobile radio stations to said base station on said control channel,   transmitting from said base station to said one of said plurality of mobile radio stations on said control channel a command to go to said additional signalling channel,   carrying out a user data transmission on said additional signalling channel, while transmitting control messaging on said control channel.   
     
     
       10. A method according to claim 9, comprising a further step of allowing two or more of said mobile radio stations to simultaneously communicate on said additional signalling channel.   
     
     
       11. A method according to claim 9, comprising a further step of controlling the number of said mobile radio stations which communicate simultaneously on said additional signalling channel in such a way that an effective transmission rate per a mobile radio station on said additional signalling channel is equal to or higher than a predetermined threshold.   
     
     
       12. A method according to claim 9, comprising further steps of detecting end of the user data transmission on said additional signalling channel,   transmitting from said base station to said one of said plurality of mobile radio stations on said additional signalling channel a command to go back to said control channel.   
     
     
       13. A method according to claim 9, comprising further steps of detecting end of the user data transmission on said additional signalling channel,   allowing said one of said plurality of mobile stations to stay on said additional signalling channel for a limited period of time in order to wait for a new user data transmission.